Supercritical fluids as solvents for enzymatic reactions

Enzymes may act in different solvent systems. Water as the solvent in vivo may be replaced partially or mostly with other solvents, such as micro-emulsions, organic solvents, reversed micelles, ionic liquids and supercritical fluids (SCFs).Several types of enzymatic reactions were performed in SCFs. Influence of SCFs on enzyme stability and activity is presented on different exampleson different reaction systems (hydrolysis, transesterification...) and on the use of non-immobilized (Subtilisin carlsberg, Aspergillus niger...) as well as immobilized enzymes. Several types of high-pressure enzymatic reactors (batch-, stirred-tank-, extractive semibatch-, recirculating batch-, semicontinuous flow-, continuous packed-bed-, and continuous-membrane reactors) have been used for the performance of enzymatic reactions. In the studies on stability of biocatalysts in a high-pressure batch-stirred tank reactor changes in biocatalysts activity due to pressurization/depressurization steps were observed. Interesting alternative to overcome this inconvenience is the use of the high-pressure continuous membrane reactors, where just single compression and expansion step is necessary.Encimi so lahko aktivni v različnih okoljih. Vodo, kot topilo in vivo, lahko delno ali v celoti nadomestimo z drugimi topili, kot somikro-emulzije, organska topila, reverzni miceliji, ionske tekočine in superkritični fluidi (SCFs). V SCFs so bile izvedene mnoge encimsko katalizirane reakcije. Vpliv SCF na stabilnost in aktivnost encima je v članku predstavljen na različnih primerihz uporabo različnih reakcijskih sistemov (hidroliza, transesterifikacija ...), z uporabo prostih (Subtilisin carlsberg, Aspergillus niger …) in imobiliziranih encimov. Za izvedbo encimsko kataliziranih reakcij se uporabljajo naslednji tipi visokotlačnih encimskih reaktorjevšaržni mešalni, ekstrakcijski polšaržni, recirkulacijski šaržni, polkontinuirani pretočni, kontinuirani z nasutim slojem biokatalizatorja in kontinuirani membranski reaktorji. Študije stabilnosti biokatalizatorja v visokotlačnem šaržnem mešalnem reaktorju so pokazale, da se aktivnost biokatalizatorja spreminja zaradi kompresije/dekompresije po vsaki šarži. Temu se lahko izognemo z uporabo visokotlačnega kontinuiranega membranskega reaktorja